Start 'Em & Sit 'Em is the ultimate look at the weekly NFL matchups and how they'll affect your fantasy football team. Sleeper alert features an under-the-radar player who could produce good numbers. Owners beware features a regular fantasy starter who could fail to meet expectations based on the strength of his opponent. Obvious fantasy starters like Aaron Rodgers and Arian Foster will not be featured in this column. For your final lineup decisions, check our lineup rankings.

Start of the week

Vikings defense vs. Arizona Cardinals: The Vikings defense has been a surprise in fantasy land this season, ranking among the top 12 units based on fantasy points after six weeks. Defenses facing the Cardinals and their porous offensive line have averaged close to 10 fantasy points per game, so starting these Purple People Eaters is well worth considering if you need a defense.

Start 'em

Patriots defense vs. New York Jets: The Patriots will be fired up after last week's loss to the Seattle Seahawks, so look for a big effort at home against the Jets. Mark Sanchez is no stranger to turning the football over, so the P-Men will no doubt be aggressive in trying to shut him down. This is also a huge AFC East battle, so New England will no doubt bring it's "A" game.

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Steelers defense at Cincinnati Bengals: The Steelers defense has not been a factor in fantasy land this season, scoring the seventh-fewest fantasy points at the position. Still, you can do worse during the bye weeks than roll the dice on them against Andy Dalton and the Bengals. Defenses have combined to score the sixth-most fantasy points against these cats from the Queen City.

Sleeper alert - Panthers defense vs. Dallas Cowboys: With six different teams on a bye, chances are you could be forced to start a defense you wouldn't have started otherwise. Enter the Panthers, who face a Dallas Cowboys team that has struggled to protect Tony Romo all year. What's more, opposing defenses facing the Boys from Big D have scored the second-most fantasy points.

Sit of the week

Jets defense at New England Patriots: The Men in Green put up a solid stat line last week, scoring 16 fantasy points in a blowout win over the Indianapolis Colts. However, that's not likely to be the case in New England. Opposing defenses that have gone up against Tom Brady's offense have combined to score the second-fewest fantasy points this season. That's not good.

Sit 'em

Giants defense vs. Washington Redskins: Much like the Jets, the G-Men put up a monster stat line (19 fantasy points) in Week 6. So while you might be tempted to start them again with six teams on a bye, just keep in mind that defenses going up against Robert Griffin III and the upstart Redskins offense have combined to score the fourth-fewest fantasy points in 2012.

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Mike Williams joined the NFL Fantasy LIVE crew and shared why he's having such success in 2012. (Click image for further analysis.)

Saints defense at Tampa Bay Buccaneers: You might look at this week's matchup against the Bucs and think the Saints could be a sleeper unit. Well, think again. Opposing defenses have combined to score an average of just 6.20 fantasy points per game against Josh Freeman and crew. What's more, New Orleans ranks a meager 25th in fantasy points among defensive units in 2012.

Owners beware - Ravens defense at Houston Texans: The Ravens defense suffered two huge losses last week, as linebacker Ray Lewis (triceps) and cornerback Lardarius Webb (knee) were lost for the season. With linebacker Terrell Suggs also still out, this unit now has little to offer from a fantasy perspective. This weekend's AFC road matchup against the Texans isn't very favorable either.